Vegetable garden fertilizer

Asked April 24, 2020, 12:19 PM EDT

Could you perhaps advise without a soil test: My vegetable garden has great green growth every year, but I have noticed a drop in the number of flowering buds and fruiting. This is especially with bush and pole beans. My potatoes are acting the same way; large amount of green growth, less potato production. I currently use a 16-16-16 commercial fertilizer. Am I getting plenty of nitrogen to support plant growth, but not enough P or K to support flowering and vegetable production? I do apply a light dose of lime every winter. Thanks for your opinion. Rick Steel

Tillamook County Oregon

1 Response

The beans and pole beans may be flowering less (or not all) due to too much nitrogen in the soil.. They are legumes - their roots have a symbiotic relationship with soil microbes (rhizobia) that fixes nitrogen from the air in the soil. Other contributors could be not enough full sun (beans need at least 6 hrs/day) and low soil temperature (need 60 deg F or higher for best production). You might consider reducing your nitrogen fertilizer component.

With respect to the potatoes, excess nitrogen in the soil will also inhibit potato tuber development as the energy is diverted to leafy growth. Potatoes typically need less nitrogen fertilizer unless you notice early leaf yellowing. Potatoes also like more acidic soils (usually between 4.8-6.5). Your yearly application of lime may be slowly reducing the acidity of the soil and that may be reducing potato yield.

The only way to know for sure about your soil's fertility is to get samples analyzed. If you decide to, here are some OSU Extension publications that are useful in this regard:

"A Guide to Collecting Soil Samples for Farms and Gardens"
https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/ec628.pdf

"Analytical Laboratories Serving Oregon"
https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/em8677.pdf